1. Field of the Invention
The present invention relates to sensors, e.g., in-flight sensors on board an aircraft, and more particularly to detecting the content of clouds.
2. Description of Related Art
Airborne volcanic ash is a serious threat to aircraft safety, as evidenced by the flame-out of all four engines of KLM Flight 867 in 1989, and a major disruption to air traffic, as was apparent during the eruption of the Iceland volcano Eyjafjallajokull in 2010. While satellites and meteorology stations report dangerous levels of ash to air traffic controllers, a sensor on board the aircraft to alert pilots of the presence of hazardous levels of ash is highly desirable. Satellite scans of a particular area are typically updated only twice per day, and meteorology stations sample the air over a limited angle above the station.
Several references describe various in-situ apparatuses and methods for determining the presence of large water droplets and icing conditions from an aircraft. However none of these references describe methods or devices for determining the presence of volcanic ash which is potentially as hazardous to an aircraft in-flight. The closest prior art is U.S. Pat. No. 7,986,408 owned by Rosemount Aerospace, Inc., hereby incorporated by reference in its entirety, which describes an airborne laser sensor for detecting and distinguishing liquid water droplets from ice crystals using circularly polarized light.
Such conventional methods and systems have generally been considered satisfactory for their intended purpose. However, there is still a need in the art for an in-flight detection systems and methods that allow for improved detection of cloud content, including volcanic ash. There also remains a need in the art for such a systems and methods that are easy to make and use. The present disclosure provides a solution for these problems.